Although absorbent articles, such as sanitary napkins or panty liners, have improved a lot the last years with respect to various features like protection and comfort in use, there is still a consumer need for further improvements in these two directions.
Indeed, there exists a real consumer need for absorbent articles, typically for feminine protection articles, having improved liquid handling properties, namely enhanced liquid distribution properties and a liquid capacity high enough for use without consumer fears of leakage or staining especially after prolonged period of wearing time, yet which are thin and flexible, thereby offering enhanced fit and comfort.
It is thus an object of the present invention to provide absorbent articles, preferably those for feminine protection, which provide enhanced distribution, absorption and retention of body fluid not only upon first contact with body fluid discharge but also upon additional subsequent body fluid discharge, thereby making the wearing experience more pleasant over prolonged period of time, and hence improving comfort. It is another object of the present invention to provide such a feminine protection article which further promotes a continuously self-conforming anatomical cooperation of the article to the wearer during various activities (e.g. sport). It is an additional object of the present invention to provide such a feminine protection article which further offers enhanced fit, comfort and a low degree of awareness.
It has now been found that all above mentioned objects are met by providing absorbent articles, like sanitary napkins and panty liners, comprising a topsheet, a backsheet and an absorbent element positioned between said topsheet and said backsheet, said element comprising a storage layer which comprises a liquid absorbent thermoplastic composition. This composition comprises a polymeric base material having particles of water-insoluble water swellable absorbent material dispersed therein, said composition is configured in a plurality of unattached spaced apart zones.
In one embodiment herein the liquid absorbent thermoplastic composition has a total absorption capacity towards saline solution of at least 2 grams/gram. In another embodiment herein the liquid absorbent thermoplastic composition represents at least 15% by weight of the total weight of the absorbent element. Most preferred executions herein combine this two features.
Advantageously the absorbent articles of the present invention comprising a storage layer with said unattached spaced apart zones of liquid absorbent thermoplastic composition exhibit faster and enhanced fluid distribution as well as enhanced fluid acquisition and retention, this not only upon first contact with body fluid but also especially when submitted to subsequent body fluid discharge versus absorbent articles being different from the ones of the present invention only in that they comprise a storage layer made of the same liquid absorbent thermoplastic composition but configured in continuous manner (e.g., covering in continuous manner almost the whole surface area between the topsheet and backsheet of the article) as opposed to discontinuous. The interstitial area between the unattached spaced apart zones of liquid absorbent thermoplastic composition (also called herein transport regions) facilitate and promote the flow of body fluid towards said unattached zones as well as the absorption of body fluid by said zones. In other words, once body fluid reaches the absorbent element, namely the storage layer, the distribution speed of the body fluid between the unattached zones is higher than the absorbency speed of the water swellable absorbent material comprised in said zones, resulting thereby in faster and enhanced distribution of fluid in the so-called transport regions of the article. Without to be bound by any theory it is believed that this is due to the low absorption kinetic of the absorbent material being entrapped into the polymeric base material in comparison to free absorbent material. When the absorption speed of absorbent material becomes predominant versus the distribution speed of the fluid in the so called transport regions, the fluids are absorbed by the absorbent material in the unattached spaced apart zones, thereby lowering the amount of fluid present in the transport regions and even emptying said regions. Hence upon subsequent discharge of body fluid within the article, the transport regions are able to fulfill once more their function of fluid distribution, resulting in more effective use of total amount of absorbent material present in the article. Indeed the gel blocking phenomenon is reduced and hence a better use of total absorption capacity of the absorbent material is obtained according to the present invention. Actually it has surprisingly been found that the fluid acquisition upon subsequent body fluid discharge in the article of the present invention is equal or even better than upon first fluid discharge. Without to be bound by theory it is believed that after the first body fluid discharge the absorbent element, namely storage layer, due to its outstanding fluid distribution properties towards increased effective total surface area used in the article per the so called transport regions and effective fluid absorption and retention properties of the storage zones becomes wetted upon enlarged surface area, hence more hydrophilic resulting in overall more effective fluid acquisition upon subsequent fluid discharge. In other words, the subsequent body fluid discharge triggers the acquisition capacity and speed, the absorbent material being much more available to absorb fluid.
Advantageously the present invention allows for versatility in positioning of the plurality of unattached spaced apart zones of said liquid absorbent thermoplastic composition. Indeed the present invention allows to target the position of the plurality of unattached spaced apart zones and hence of the absorbent material where needed in the absorbent element/article and hence optimizes the ratio total amount of absorbent material and liquid absorption capacity. The total amount of particles of water-insoluble water swellable absorbent material present in said spaced apart zones of the absorbent element will be more efficiently utilized resulting in improved absorption characteristics of the absorbent element. As a result, the absorbent article can be configured with a thinner structure which is capable of absorbing larger amount of body fluid and more flexible structure. The thinner and more flexible structure can in turn provide improved fit and comfort to the wearer.
Advantageously the absorbent element, namely storage layer, of the articles of the present invention delivers outstanding protection with absence of water swellable absorbent material particle spillage in both dry and wet condition. The powder spillage free property of the thermoplastic composition used herein is beneficial for easier processability and handling in plant as well as for safety criteria. Also the swollen absorbent material in wet condition is less liable to escape the spaced apart zones of the storage layer. Without to be bound by theory it is speculated that cohesion of polymeric base material is able to maintain location of the absorbent materials also after swelling, thereby accommodating the increased volume of the swollen material.
Advantageously the use of the liquid absorbent thermoplastic composition herein fulfill besides the absorption properties also the function of adhering adjacent/surrounding layers of the article together. Hence the need of conventional adhesive glue to adhere storage layer to adjacent layers for example backsheet and topsheet can be avoided.
In an embodiment herein wherein the backsheet of the article is a breathable backsheet, it has been found that the absorbent element according to the present invention, especially for those embodiments wherein the absorbent element comprises, as the storage layer, the liquid absorbent thermoplastic composition described herein configured in a plurality of unattached spaced apart zones, is particularly advantageous as besides above mentioned benefits, its use also results in improved air and water vapor permeability of the absorbent article both in dry and wet condition.